SENTRY KEY IMMOBILIZER SYSTEM
The Sentry Key Immobilizer System (SKIS) is
available as a factory-installed option on this vehicle.
It is designed to provide passive protection against
unauthorized vehicle use by disabling the engine,
after two (2) seconds of running, whenever an invalid
key is used to start the vehicle. The SKIS is active
whenever the ignition is on and does not require any
customer intervention. The primary components of
the system are the Sentry Key Immobilizer Module
(SKIM), Sentry Key (ignition key with a transponder
molded into the head), indicator light, and the Powertrain
Control Module (PCM). The SKIM is mounted
to the steering column with the molded, integral
antenna mounted on the trim ring surrounding the
ignition lock cylinder. The indicator light, is located
in the instrument cluster.
SENTRY KEY IMMOBILIZER SYSTEM
The SKIS includes keys from the factory which are
pre-programmed. Each SKIM will recognize a maximum
of eight Sentry Keys. If the customer would
like to own additional keys other than those provided
with the vehicle, they can be purchased from any
authorized dealer. These keys must be programmed
to the SKIM on the vehicle in order for the system to
recognize them as valid keys. This can be done by
the dealer with a DRB IIIt scan tool or by a customer
if this feature is available in their market and
they have two (2) valid keys already available to
them.
DESCRIPTION
The Sentry Key Immobilizer System (SKIS) uses a
transponder chip that is integral to each ignition key
(Fig. 3) to communicate with the Sentry Key Immobilizer
Module (SKIM). Ignition keys are supplied
with the vehicle when it is shipped from the factory.
The transponder chip is undermolded within the
head of the key. This undermold is hidden beneath
an overmolded rubber cap.
OPERATION
Each Sentry Key transponder has a unique transponder
identification code programmed into it by the
manufacturer. The Sentry Key Immobilizer Module
(SKIM) has a unique “Secret Key” code programmed
into it by the manufacturer. When a Sentry Key
transponder is programmed into the memory of the
SKIM, the SKIM learns the transponder identification
code from the transponder, and the transponder
learns the “Secret Key” code from the SKIM. Each of
these codes is stored within the transponder and in
the nonvolatile memory of the SKIM. Therefore,
blank keys for the SKIS must be programmed by and
into the SKIM, in addition to being cut to match the
mechanical coding of the ignition lock cylinder.
The Sentry Key’s transponder is within the range
of the SKIM’s transceiver antenna ring when it is
inserted into the ignition lock cylinder. When the
ignition switch is turned to the ON position, the
SKIM communicates with the Sentry Key via a radio
frequency (RF) signal. The SKIM determines if a
valid key is present based on the information it
receives from the Sentry Key. If a valid key is
detected, that fact is communicated to the PCM via
the PCI bus and the vehicle is allowed to continue
running. If an invalid key is received by the PCM or
no status at all is communicated, the vehicle will
stall after two (2) seconds of running. The indicator
light will be flashing at this point. The Sentry Key’s
transponder can not be repaired. If it is faulty or
damaged, it must be replaced.
See? Hope that clears everything up for you.
I know all about that. They say it can be reproduced and downsized. But that time is not yet. Until some shows me a car actually stolen this way, it's still just an experiment. Sucessful, but not a threat to any car yet. 
